The present invention relates to a timing device for pneumatic signals of the kind comprising a pneumatic motor having gearing which is brought into coupled engagement with a timer when an input signal occurs so that a control member associated with the timer, which can be set for a desired delay between the input signal and an output signal, is moved from an initial position which determines the length of delay to a terminal position which marks the end of the delay and at which the output signal is produced.
German Offenlegungsschrift No. 1 673 562 discloses an entirely pneumatically operated timing device for pneumatic signals which has a pneumatic motor. This motor has gearing which, when an input signal occurs, is brought into coupled engagement with a timer so that a control member associated with the timer, which can be set for a desired delay between the input signal and an output signal, is moved from an initial position which determines the length of delay to a terminal position which marks the end of the delay and at which the output signal is produced.
This known timing device has a number of disadvantages. Firstly, it takes up a considerable amount of space and requires a considerable amount of material, since it contains, inter alia, a switchable and thus relatively complicated clutch coupling device which drives a shaft carrying the member which changes over with a delay to produce the output signal. Also provided is an additional valve which is operated with a delay by the change-over member so as to allow the output signal to come into being. Furthermore, the arrangement for pre-selecting the delay is of rather complicated and expensive construction since it consists of a quite large toothed disc with a setting pointer and of a pinion or worm which actuates this disc and which is adjusted by a hand-operated rotary knob or the like. This means that it takes quite a long time even to set the delay. Thus, it will be understood that this known device requires a considerable number of parts and takes up a considerable amount of space. A further disadvantage is that the clutch coupling device detracts from the reliability of the device in operation since the repeatability of the pre-selected delay cannot be maintained with sufficient accuracy should slip occur.
It is an object of the invention to provide a simple and compact pneumatic timing device which is cheap to make and quick to adjust, in which in addition there is little wear and an assurance of reliability and which operates with a low level of friction.